Power amplifier circuit and front end circuit

ABSTRACT

A power amplifier circuit (DIPPA), comprising a driver stage (DR) which is applicable to provide a preamplified driver signal (S_DR) dependent on a predetermined transmit signal. The power amplifier circuit (DIPPA) comprises also a frequency selector (DIP) which is electrically coupled to the driver stage (DR) and which is applicable to separate the driver signal (S_DR) into a first and second signal (S —   1 , S —   2 ). The first signal (S —   1 ) is associated to a first predetermined and the second signal (S —   2 ) is associated to a second predetermined frequency band. The power amplifier circuit (DIPPA) comprises at least a first and second power amplifier stage (PA 1 , PA 2 ). The first and second power amplifier stage (PA 1 , PA 2 ) are electrically coupled to the frequency selector (DIP). The first and second power amplifier stage (PA 1 , PA 2 ) is operable to provide a first and second amplified signal (S_A 1 , S —   2 ), respectively, dependent on the first and second signal (S —   1 , S —   2 ), respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage of International ApplicationNo. PCT/EP2009/066355, filed Dec. 3, 2009, which is incorporated hereinby reference in its entirety.

The present invention relates to a power amplifier circuit and a frontend circuit comprising the power amplifier circuit.

Front end modules are generally known for the transmission and receptionof wireless communication signals for example in wireless communicationdevices as for example cellular phones. In this respect Universal MobileTelecommunication System (UMTS) and GSM are generally known wirelesscommunication standards.

The object of the invention is to provide a power amplifier circuit anda front end circuit, which facilitates an efficient operation and whichis cost-effective.

These objects are achieved by the features of the independent claims.Aspects and several embodiments are subject to the dependent claims.

The invention according to a first aspect is distinguished by a poweramplifier circuit for wireless communication devices, which comprises adriver stage with an input terminal and an output terminal. The driverstage is applicable to provide a preamplified driver signal at itsoutput terminal dependent on a predetermined transmit signal at itsinput terminal. The power amplifier circuit further comprises afrequency selector with an input terminal and at least two outputterminals. The frequency selector is electrically coupled to the outputterminal of the driver stage via its input terminal and is operable toseparate at least a first signal and a second signal from the driversignal. The first signal is associated to a first predeterminedfrequency band and the second signal is associated to a secondpredetermined frequency band. The power amplifier circuit also comprisesat least a first power amplifier branch and a second power amplifierbranch. Each power amplifier branch comprises an input terminal and anoutput terminal. The input terminal of the first power amplifier branchis electrically coupled to the first output terminal of the frequencyselector. The input terminal of the second power amplifier branch iselectrically coupled to the second output terminal of the frequencyselector. The first power amplifier branch is operable to provide afirst amplified signal at its output terminal dependent on the firstsignal and the second power amplifier branch is operable to provide asecond amplified signal at its output terminal dependent on the secondsignal.

This contributes to an efficient power amplifier circuit, which may beused for example in cellular phones, wireless network cards, etc. Thepower amplifier circuit may be supplied with transmit signals comprisingsignals of the first and second frequency band, as for example UMTS orGSM frequency bands. The power amplifier circuit may be used only fordata transmission in transmit direction. The transmit directioncorresponds to a signal direction from the input terminal of the driverstage to the particular output terminals of the first and second poweramplifier branch.

Each of the at least first and second power amplifier branch maycomprise at least one power amplifier stage, as for example a radiofrequency amplifier stage. Each power amplifier branch is operable toincrease the output power of the signals to be transmitted via anantenna.

The frequency selector may be a diplexer, diplexing the preamplifiedsignal provided by the driver stage into the first and second signal inthe transmit direction of the power amplifier circuit. The poweramplifier circuit may comprise more than two power amplifier branches.The number of output terminals of the particular frequency selectorcorresponds to the number of power amplifier branches. When processingfor example signals of three frequency bands, the frequency selector maybe a triplexer, providing a particular signal of a predeterminedfrequency band at each of its three output terminals. The frequencyselector may be a passive or active element with additional poweramplifiers.

Each power amplifier branch is associated to a predetermined frequencyband. By this, each power amplifier branch and its components, as forexample the power amplifier stages, may be optimized in amplifyingsignals of the associated frequency band. This contributes to increasingthe efficiency of the power amplifier circuit.

In an embodiment of the first aspect the driver stage comprises at leastone wideband amplifier which is applicable to preamplify the suppliedpredetermined transmit signal over a wide range of frequencies. The widerange of frequencies covers the at least first and second predeterminedfrequency bands. The driver stage comprises only one input terminal andone output terminal and is applicable to preamplify signal parts of thetransmit signal associated to the first and second frequency band. Theat least one wideband amplifier of the driver stage may be a travellingwave amplifier.

In a further embodiment of the first aspect the frequency selectorcomprises at least two power amplifiers, which are operable to amplifythe driver signal and/or the first signal and/or the second signal. Thefrequency selector may comprise right handed transmission line elementsand/or composite right left handed transmission line elements with poweramplifiers electrically arranged between those transmission lineelements. This contributes to ensuring a separation of the first andsecond signal from the preamplified driver signal.

In a further embodiment of the first aspect each of the first and/orsecond power amplifier branch comprises at least one narrow band poweramplifier. While a wideband amplifier is operable to boost signals overa wide range of frequencies, the narrow band amplifier is operable toboost only a signal in a specific narrow range of frequencies, as forexample the first frequency band and second frequency band,respectively. All other frequencies are excluded from amplification bythe narrow band power amplifier. The narrow-band amplifier may alsocomprise linear characteristics and is operable to output signals withonly limited or no harmonic distortion. This basically preventsharmonics in the particular output signal of the power amplifiercircuit. Furthermore, the narrow-band amplifier may also constituteharmonic tuning and by this, may be operable to suppress harmonics dueto non-linearities of the previous components with respect to thetransmit direction.

In a further embodiment of the first aspect the power amplifier circuitfurther comprises at least a first and second bypass-path. The firstbypass-path is associated to the first power amplifier branch and thesecond bypass-path is associated to the second power amplifier branch.The particular bypass-path is operable to bypass the input terminal andoutput terminal of the particular power amplifier branch.

Additionally, the power amplifier components of the particular poweramplifier branch, as for example the power amplifier stage, may bedecoupled from their supply voltage if the particular bypass isconstituted. This contributes to reducing the power consumption of thepower amplifier circuit. For activation or deactivation of the bypass,the particular bypass-path may comprise a particular switching element,for example a transistor, which may be controlled by a control logic ofthe particular wireless communication device.

In a further embodiment of the first aspect the driver stage and thefrequency selector or the frequency selector and the first poweramplifier stage and second power amplifier stage or the driver stage andthe frequency selector and the first power amplifier branch and secondpower amplifier branch are integrated on a single-chip. This contributesto reducing a space requirement of the power amplifier circuit. Thepower amplifier circuit as single-chip may be realized for example inGaAs BiFET technology which is suitable for high-frequency applications.But also other suitable technology may be used.

The invention according to a second aspect is distinguished by a frontend circuit for a wireless communication device which comprises a poweramplifier circuit according to the first aspect. Furthermore, the frontend circuit comprises at least a first duplexer and a second duplexer.Each of the first duplexer and second duplexer comprises an inputterminal and an output terminal. The input terminal of the firstduplexer is electrically coupled to the output terminal of the firstpower amplifier branch and the input terminal of the second duplexer iselectrically coupled to the output terminal of the second poweramplifier branch. Each of the first duplexer and second duplexer isoperable to pass signals from its input terminal to its output terminal.The front end circuit further comprises a common antenna which iselectrically coupled to the output terminal of the first duplexer and tothe output terminal of the second duplexer.

Due to the use of the efficient power amplifier circuit, the front endcircuit also facilitates an efficient operation. The front end circuitmay be used in multiple-band mobile handsets for the 2G/3G/4G standards.The particular wireless communication device may also comprise more thanone power amplifier circuit. The particular duplexer may comprisemultiple band pass filters with one being configured to pass for examplea first signal of a predetermined first frequency band, for exampletransmit frequency band, and to filter a second signal of apredetermined second frequency band, for example a receive frequencyband. The particular duplexer may also be a switching element. In thetransmit direction the particular duplexer is operable to pass signalsfrom the particular power amplifier branch from its input terminal tothe common antenna via its output terminal.

The terms “input terminal” and “output terminal” relate to the transmitdirection of the power amplifier circuit and front end circuit.

Each of the first duplexer and second duplexer may comprise a transmitfilter and a receive filter. The transmit filter of each duplexercomprises an input terminal and an output terminal. The input terminalof the transmit filter of the first duplexer is electrically coupled tothe output terminal of the first power amplifier stage and the outputterminal of the transmit filter of the first duplexer is electricallycoupled to the common antenna. The input terminal of the transmit filterof the second duplexer is electrically coupled to the output terminal ofthe second power amplifier branch and the output terminal of thetransmit filter of the second duplexer is electrically coupled to thecommon antenna.

In an embodiment of the second aspect the front end circuit comprises anantenna multiplexer with at least a first input terminal and a secondinput terminal and a single output terminal. The output terminal of theantenna multiplexer is electrically coupled to the common antenna. Thefirst input terminal of the antenna multiplexer is electrically coupledto the output terminal of the first duplexer, in particular of thetransmit filter of the first duplexer. The second input terminal of theantenna multiplexer is electrically coupled to the output terminal ofthe second duplexer, in particular of the transmit filter of the secondduplexer. The antenna multiplexer is operable to combine the signalsoutputted from the first duplexer and second duplexer and to provide itto the common antenna in the transmit direction. The multiplexer may bea frequency selector according to the first aspect. The multiplexer mayfor example be a diplexer, triplexer, etc. The number of input terminalsof the multiplexer corresponds to the number of duplexer electricallycoupled to each input terminal of the multiplexer.

In the following, the disclosure is described in further detail withreference to the drawings, wherein

FIG. 1 front end circuit,

FIG. 2 front end circuit with power amplifier circuit,

FIG. 3 frequency selector,

FIG. 4 another frequency selector.

Elements of the same design and function that appear in differentillustrations are identified by the same reference character.

FIG. 1 depicts an embodiment of a front end circuit FEM which may beused in wireless or mobile communication devices as for example cellularphones in GSM or UMTS-networks.

The front end circuit FEM comprises a power amplifier circuit DIPPA, afirst duplexer LBDUP and a second duplexer HBDUP and a common antennaANT.

The power amplifier circuit DIPPA may be electrically coupled to atransceiver TXRX, for example a WCDMA-transceiver, of the particularwireless communication device. In a transmit direction, the transceiverTXRX supplies transmit signals associated to a predetermined frequencyband to an input terminal of the power amplifier circuit DIPPA. In areceive direction, received signals typically bypass the power amplifiercircuit DIPPA and are directly routed to a receive terminal of thetransceiver TXRX.

The power amplifier circuit DIPPA comprises a first output terminal anda second output terminal. The first output terminal and second outputterminal are electrically coupled to an input terminal of the firstduplexer and second duplexer LBDUP, HBDUP, respectively. The firstoutput terminal of the power amplifier circuit DIPPA is associated to afirst frequency band, for example a transmit frequency band of GSM 900covering a frequency range from 876 MHz to 915 MHz. The second outputterminal of the power amplifier circuit DIPPA is associated to a secondfrequency band, for example a transmit frequency band of GSM 1900covering a frequency range from 1850 MHz to 1910 MHz. The poweramplifier circuit DIPPA provides a first amplified signal S_A1 and asecond amplified signal S_A2 at its first output terminal and secondoutput terminal, respectively.

The power amplifier circuit DIPPA may also comprise more than two outputterminals and may also be electrically coupled to more than twoduplexers.

The output terminal of each of the first duplexer LBDUP and secondduplexer HBDUP is electrically coupled to the common antenna ANT. Thecoupling to the common antenna ANT may be established by an additionalantenna multiplexer ADIP which is electrically arranged between theoutput terminals of the first and second duplexer LBDUP, HBDUP and aterminal of the common antenna ANT. The antenna multiplexer ADIP may bea diplexer. In the transmit direction, the provided transmit signals ofthe first frequency band and/or second frequency band are routed throughthe antenna multiplexer ADIP to the common antenna ANT.

Alternatively, the antenna multiplexer ADIP may be a conventionalswitch. Furthermore, the antenna multiplexer ADIP may be a balanceddiplexer.

In the transmit direction, the first duplexer LBDUP is operable to routethe first amplified signal S_A1 from its input terminal to its outputterminal. For this purpose, the first duplexer LBDUP may comprise atransmit filter routing the first amplified signal S_A1 from the inputterminal to the output terminal of the first duplexer LBDUP. The secondduplexer HBDUP is operable to route the second amplified signal S_A2from its input terminal to its output terminal. For this purpose, thesecond duplexer HBDUP may comprise another transmit filter routing thesecond amplified signal S_A2 from the input terminal to the outputterminal of the second duplexer HBDUP.

In the receive direction, received signals are typically associated todifferent frequency bands than the associated transmit frequency bands,for example the receive frequency band of the GSM 900 covers frequenciesfrom 921 to 960 MHz and the receive frequency band of the GSM 1900covers frequencies from 1930 to 1990 MHz. Each of the first and secondduplexer LBDUP, HBDUP may also comprise multiple band pass filters. Oneof the band pass filters, for example the transmit filter, may beconfigured to pass only signals of the particular transmit frequencyband in the transmit direction. Another band pass filter, for example areceive filter, may be configured to only pass signals of the particularreceive frequency band of the particular frequency band in the receivedirection, whereas the passed signals of the particular receivefrequency band are directly routed to the particular receive terminal ofthe transceiver TXRX and not to the input terminal of the particularduplexer LBDUP, HBDUP. This is illustrated in FIG. 1 by a separatereceive signal path S_R routing the signals of the first receivefrequency band from the first duplexer LBDUP directly to the transceiverTXRX.

FIG. 2 depicts a further embodiment of the front end circuit FEM withthe power amplifier circuit DIPPA which comprises a driver stage DR, afrequency selector DIP and a first power amplifier branch and a secondpower amplifier branch. The first power amplifier branch comprises forexample a first amplifier stage PA1 and the second power amplifierbranch comprises for example a second power amplifier stage PA2.

The driver stage DR comprises one input terminal and one outputterminal. The input terminal of the driver stage DR is electricallycoupled to an output terminal of the transceiver TXRX and by thissupplied by the transmit signals from the transceiver TXRX. The driverstage DR may be operable to process, e.g. preamplify, the suppliedtransmit signals into appropriate driver signals S_DR which are furtherprocessed by subsequent components of the power amplifier circuit DIPPA.The driver stage DR may be a wideband driver which is operable toprocess transmit signals over a wide range of frequencies. For thispurpose, the driver stage DR may comprise a wideband amplifier, forexample a traveling wave amplifier. In particular, the driver stage DRmay be operable to process transmit signals at least of the firstfrequency band and of the second frequency band.

The driver stage DR provides the processed driver signal S_DR at itsoutput terminal which is electrically coupled to an input terminal PINof the frequency selector DIP (FIG. 3). The frequency selector DIPfurther comprises a first and second output terminal (POUT1, POUT2)(FIG. 3). The frequency selector DIP is operable to divide transmitsignals provided at its input terminal PIN into a first signal S_1 atits first output terminal POUT1 and into a second signal S_2 at itssecond output terminal POUT2. The first signal S_1 and the second signalS_2 are associated to signals of the first frequency band and secondfrequency band, respectively. Ideally, the frequency selector DIP isoperable to transfer none of the signals of the first frequency band toits second output terminal POUT2 and none of the signals of the secondfrequency band to its first output terminal POUT1. The frequencyselector DIP is at least operable to provide dampened signals of thefirst frequency at its second output terminal POUT2 and is at leastoperable to provide dampened signals of the second frequency at itsfirst output terminal POUT1.

The frequency selector DIP may be a passive or active element withadditional power amplifiers as illustrated in FIG. 3. FIG. 3 depicts anexemplary diplexing traveling wave amplifier as frequency selector DIP.The frequency selector DIP comprises several power amplifiers PA3,several first type transmission line elements TL1 and several secondtype transmission line elements TL2. The input terminal PIN and thefirst and second output terminal POUT1, POUT2 may be represented byparticular resistors R which are electrically coupled to a referencepotential GND.

The first type transmission line elements TL1 are for example righthanded structures (RH-TL) with each being operable to shift a phase of asignal dependent on the signal's frequency. Each first type transmissionline element TL1 may for example be a conventional transmission linerepresenting telegraph equations.

The second type transmission line elements TL2 may be for examplecomposite right/left handed meta-material-structures (CRLH-TL) with eachbeing operable to predetermine a slope and phase of a signal dependenton the signal's frequency.

Furthermore, such transmission lines may be dimensioned in such a waythat a signal transportation direction depends on the signal'sfrequency.

The frequency selector DIP according to FIG. 3 comprises multipletransmission line units TLU, with each comprising a first typetransmission line element TL1 and a second type transmission lineelement TL2 with both transmission line elements being electricallycoupled in parallel. The transmission line units TLU are electricallycoupled in series and by this are operable to dampen or amplify a signaldependent on the particular phase response of the first and second typetransmission line element. The particular phase response is dependent onthe signal's frequency and dependent on the dimension of the particularfirst and second type transmission line element TL1, TL2 of eachtransmission line unit TLU.

Due to this behavior of the first and second type transmission lineelements TL1, TL2, the first signal S_1 associated to the firstfrequency band is separated from the driver signal S_DR and is provideat the first output terminal POUT1 of the frequency selector DIP. On theother hand, the signal parts of the driver signal S_DR associated to thesecond frequency band are damped in such way, that a power of the secondsignal S_2 provided at the first output terminal POUT1 is significantlylower than a power of the first signal S_1. Furthermore, the secondsignal S_2 is provided at the second output terminal POUT2 with a powersignificantly higher than the power of the first signal S_1 at thesecond output terminal POUT2 of the frequency selector DIP. The poweramplifiers PA3 may be traveling wave amplifiers or transistor amplifiercircuits.

The first signal S_1 and the second signal S_2 are provided to the firstpower amplifier stage PA1 of the first power amplifier branch and to thesecond power amplifier stage PA2 of the second power amplifier branch,respectively.

In a further embodiment, the power amplifier circuit DIPPA may comprisea triplexer as frequency selector DIP. By this, the frequency selectorDIP comprises three output terminals POUT1, POUT2, POUT3, each beingelectrically coupled to a particular power amplifier branch.

FIG. 4 depicts an exemplary embodiment of a triplexing traveling waveamplifier which may be used as frequency selector DIP. The frequencyselector DIP further comprises a first, second and third typetransmission line element TL1, TL2, TL3, wherein the first and secondtransmission line element TL1, TL2 may be identical to the first andsecond transmission line elements as described according to FIG. 3.

The third type transmission line element TL3 may also be a compositeright/left handed meta-material-structure (CRLH-TL) which is operable topredetermine a slope and phase of a signal dependent on the signal'sfrequency. Compared to the second type transmission line element TL2,the third type transmission line element TL3 may differ in its magnitudeand phase response. The first type transmission line element TL1 mayhave low pass characteristics while the second type transmission lineTL2 may have high pass characteristics.

Due to the dampening and amplifying features of the particular first,second and third type transmission line elements TL1, TL2, TL3, thefirst, second and a third signal is separated from the particular driversignal S_DR provided by the driver stage DR at the input terminal PIN ofthe triplexer. The first signal is provided at the first output terminalPOUT1 with a power significantly higher than the power of the secondsignal and third signal. The second signal is provided at the secondoutput terminal POUT2 with a power significantly higher than the powerof the first signal and third signal. And the third signal is providedat the third output terminal POUT3 with a power significantly higherthan the power of the second signal and third signal. The optional poweramplifiers PA4 may be traveling wave amplifiers or transistor amplifiercircuits.

Alternatively, the power amplifier circuit DIPPA may comprise more thanthree power amplifier branches and a multiplexer as frequency selectorDIP with more than three output terminals. The number of outputterminals of the frequency selector DIP preferably corresponds to thenumber of power amplifier branches.

Each of the first and second power amplifier branch comprises a singleinput and output terminal. The input terminal and output terminal of thefirst power amplifier branch is coupled to an input terminal and anoutput terminal of the first amplifier stage PA1, respectively. Theinput terminal and output terminal of the second power amplifier branchis coupled to an input terminal and an output terminal of the secondamplifier stage PA2, respectively.

Each of the first amplifier stage PA1 and second power amplifier stagePA2 of the power amplifier circuit DIPPA may be a narrow-band amplifier(FIG. 2). By this, the first power amplifier stage PA1 is dimensionedwith respect to the associated first signal S_1 to be amplified and thesecond power amplifier stage PA2 is dimensioned with respect to theassociated second signal S_2 to be amplified. Due to the limited amountof components arranged behind the particular power amplifier stage PA1,PA2 in transmit direction, the particular first signal S_1 or secondsignal S_2 can be amplified and transmitted very efficiently.Additionally, the arrangement of the at least first power amplifierstage PA1 and the second power amplifier stage PA2 contributes todecreasing RF and DC losses and higher efficiency due to increasedharmonic tuning, i.e. harmonic suppression.

The first power amplifier stage PA1 is operable to provide the firstamplified signal S_A1 at its output terminal and the second poweramplifier stage PA2 is operable to provide the second amplified signalsS_A2 at its output terminal.

Additionally, the first power amplifier branch may comprise a firstbypass-path BP1 and the second power amplifier branch may comprise asecond bypass-path BP2. Each bypass-path BP1, BP2 is operable to bypassthe components, as for example the particular power amplifier stage, ofthe particular power amplifier branch, for example in a low-power modeof the front end circuit FEM. By this, the particular first signal S_1or second signal S_2 may be routed directly to the input terminal of theparticular duplexer LBDUP, HBDUP in the low-power mode without passingthe particular power amplifier stage PA1, PA2. In the low-power mode thefirst power amplifier stage PA1 and/or second power amplifier stage PA2may be decoupled from a supply voltage of the wireless communicationdevice, by this reducing the total power consumption of the front endcircuit FEM.

The first power amplifier stage PA1 and second power amplifier stage PA2may be traveling wave amplifiers in a particular narrow-bandconfiguration. But also other known narrow-band power amplifiers may beused.

In further embodiments the components of the power amplifier circuitDIPPA may be implemented as a single-chip implementation or as amulti-chip-implementation or in a multi-technology implementation,depending on the tradeoffs of performance, cost, etc. The freedom tochoose the chip and technology implementation applies for the activecomponents, as for example transistors, as well as for the passivecomponents, as for example inductors.

The present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

Reference Numerals

-   ADIP antenna multiplexer-   ANT common antenna-   BP1 first bypass-path-   BP2 second bypass-path-   DIP frequency selector-   DIPPA power amplifier circuit-   DR driver-   FEM front end circuit-   GND reference potential-   HBDUP second duplexer-   LBDUP first duplexer-   PA1, PA2 power amplifier stage-   PA3, PA4 power amplifier-   PIN input terminal-   POUT1, output terminals-   POUT2,-   POUT3-   R resistor-   S_1 first signal-   S_2 second signal-   S_A1 first amplified signal-   S_A2 second amplified signal-   S_DR driver signal-   S_R receive signal path-   TL1, TL2, transmission line elements-   TL3-   TLU transmission line unit-   TXRX transceiver

The invention claimed is:
 1. A power amplifier circuit for wirelesscommunication devices, comprising: a driver stage with an input terminaland output terminal, the driver stage being applicable to provide apreamplified driver signal at its output terminal dependent on apredetermined transmit signal at its input terminal, a frequencyselector with an input terminal and at least two output terminals, thefrequency selector being electrically coupled to the output terminal ofthe driver stage via its input terminal and being operable to separateat least a first signal and a second signal from the driver signal,whereas the first signal is associated to a first predeterminedfrequency band and the second signal is associated to a secondpredetermined frequency band, at least a first power amplifier branchand a second power amplifier branch with each comprising an inputterminal and an output terminal, whereas the input terminal of the firstpower amplifier branch is electrically coupled to the first outputterminal of the frequency selector and the input terminal of the secondpower amplifier branch is electrically coupled to the second outputterminal of the frequency selector, whereas the first power amplifierbranch is operable to provide a first amplified signal at its outputterminal dependent on the first signal and the second power amplifierbranch is operable to provide a second amplified signal at its outputterminal dependent on the second signal, and a traveling wave amplifierused to constitute the frequency selector and the driver stage.
 2. Poweramplifier circuit according to claim 1, whereas the driver stagecomprises at least one wideband amplifier which is applicable topreamplify the supplied predetermined transmit signal over a wide rangeof frequencies, whereas the wide range of frequencies covers the atleast first and second predetermined frequency band.
 3. Power amplifiercircuit according to claim 1, whereas the frequency selector comprisesat least one power amplifier which is operable to amplify the driversignal and/or the first signal and/or the second signal.
 4. Poweramplifier circuit according to claim 1, whereas each of the first and/orsecond power amplifier branch comprises at least one narrow band poweramplifier.
 5. Power amplifier circuit according to claim 1, comprisingat least a first bypass-path and a second bypass-path, whereas the firstbypass-path is associated to the first power amplifier branch and thesecond bypass-path is associated to the second power amplifier branch,whereas the particular bypass-path is operable to bypass the inputterminal and output terminal of the particular power amplifier branch.6. Power amplifier circuit according to claim 1, whereas the driverstage and the frequency selector, or the frequency selector and thefirst power amplifier branch and the second power amplifier branch, orthe driver stage and the frequency selector and the first poweramplifier branch and second power amplifier branch are integrated on asingle-chip.
 7. Power amplifier circuit according to claim 1, furthercomprising: at least a first duplexer and second duplexer, each of thefirst duplexer and second duplexer comprising an input terminal and anoutput terminal, whereas the input terminal of the first duplexer iselectrically coupled to the output terminal of the first power amplifierbranch and the input terminal of the second duplexer is electricallycoupled to the output terminal of the second power amplifier branch,whereas each of the first duplexer and second duplexer is operable topass signals from its input terminal to its output terminal, and acommon antenna being electrically coupled to the output terminal of thefirst duplexer and to the output terminal of the second duplexer. 8.Power amplifier circuit according to claim 1, wherein the traveling waveamplifier comprises multiple power amplifiers, multiple first typetransmission line elements and multiple second type transmission lineelements, wherein each of the first type transmission line elements isoperable to shift a phase of a signal dependent on the signal'sfrequency; wherein each of the second type transmission line elements isoperable to predetermine a slope and phase of a signal dependent on thesignal's frequency; wherein transmission lines including at least one ofthe first or second type transmission line elements are dimensioned sothat a signal transportation direction depends on at least the signal'sfrequency.